Re: [PATCH] media: v4l2: Initialize mpeg slice controls

[Boris Brezillon <boris.brezillon@collabora.com>]

On Wed, 29 May 2019 13:59:50 -0300
Ezequiel Garcia <ezequiel@collabora.com> wrote:

> On Wed, 2019-05-29 at 18:06 +0200, Boris Brezillon wrote:
> > On Wed, 29 May 2019 17:42:58 +0200
> > Hans Verkuil <hverkuil@xs4all.nl> wrote:
> >   
> > > On 5/29/19 5:36 PM, Ezequiel Garcia wrote:  
> > > > On Wed, 2019-05-29 at 16:41 +0200, Hans Verkuil wrote:    
> > > > > On 5/3/19 1:42 PM, Boris Brezillon wrote:    
> > > > > > Make sure the default value at least passes the std_validate() tests.
> > > > > > 
> > > > > > Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
> > > > > > ---
> > > > > >  drivers/media/v4l2-core/v4l2-ctrls.c | 20 +++++++++++++++++++-
> > > > > >  1 file changed, 19 insertions(+), 1 deletion(-)
> > > > > > 
> > > > > > diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c b/drivers/media/v4l2-core/v4l2-ctrls.c
> > > > > > index b1ae2e555c68..19d40cc6e565 100644
> > > > > > --- a/drivers/media/v4l2-core/v4l2-ctrls.c
> > > > > > +++ b/drivers/media/v4l2-core/v4l2-ctrls.c
> > > > > > @@ -1461,7 +1461,14 @@ static bool std_equal(const struct v4l2_ctrl *ctrl, u32 idx,
> > > > > >  static void std_init(const struct v4l2_ctrl *ctrl, u32 idx,
> > > > > >  		     union v4l2_ctrl_ptr ptr)
> > > > > >  {
> > > > > > -	switch (ctrl->type) {
> > > > > > +	struct v4l2_ctrl_mpeg2_slice_params *p_mpeg2_slice_params;
> > > > > > +
> > > > > > +	/*
> > > > > > +	 * The cast is needed to get rid of a gcc warning complaining that
> > > > > > +	 * V4L2_CTRL_TYPE_MPEG2_SLICE_PARAMS is not part of the
> > > > > > +	 * v4l2_ctrl_type enum.
> > > > > > +	 */
> > > > > > +	switch ((u32)ctrl->type) {
> > > > > >  	case V4L2_CTRL_TYPE_STRING:
> > > > > >  		idx *= ctrl->elem_size;
> > > > > >  		memset(ptr.p_char + idx, ' ', ctrl->minimum);
> > > > > > @@ -1486,6 +1493,17 @@ static void std_init(const struct v4l2_ctrl *ctrl, u32 idx,
> > > > > >  	case V4L2_CTRL_TYPE_U32:
> > > > > >  		ptr.p_u32[idx] = ctrl->default_value;
> > > > > >  		break;
> > > > > > +	case V4L2_CTRL_TYPE_MPEG2_SLICE_PARAMS:
> > > > > > +		p_mpeg2_slice_params = ptr.p;
> > > > > > +		/* 4:2:0 */
> > > > > > +		p_mpeg2_slice_params->sequence.chroma_format = 1;
> > > > > > +		/* 8 bits */
> > > > > > +		p_mpeg2_slice_params->picture.intra_dc_precision = 0;
> > > > > > +		/* interlaced top field */
> > > > > > +		p_mpeg2_slice_params->picture.picture_structure = 1;
> > > > > > +		p_mpeg2_slice_params->picture.picture_coding_type =
> > > > > > +					V4L2_MPEG2_PICTURE_CODING_TYPE_I;    
> > > > > 
> > > > > Oops, this isn't complete. It should still zero the p_mpeg2_slice_params
> > > > > struct first. Right now any fields not explicitly set just have whatever
> > > > > was in memory.  
> > 
> > Oops.
> >   
> > > > > Can you post a patch fixing this?
> > > > > 
> > > > >    
> > > > 
> > > > I was wondering if we want to zero all the cases, and not just
> > > > the struct types ones.    
> > > 
> > > The others either overwrite the data with the default_value, or memset
> > > the whole control (default case). It's only for these compound controls
> > > that something special needs to be done.
> > > 
> > > The code can be restructured, though: instead of break do return in all
> > > the simple type cases.
> > > 
> > > Then call memset followed by a new switch for the compound types where you
> > > need to set some fields to non-zero.  
> > 
> > memset(0) will fix the undefined val issue, the question is, is it the
> > default we want? I haven't worked on MPEG2 (just posted patches
> > Ezequiel worked on) so I can't tell.
> >   
> 
> Well, any fields where zero is not a good default, should be assigned here.
> 

That's my point: I've only assigned fields that were checked by the core
and where 0 is not a valid value. That doesn't necessarily make 0 a good
default for the other fields :P. Hence my suggestion to have someone
that knows about MPEG2 (you :)) check the other fields.